Fluorescence activated cell sorting will be utilized to: 1) Clone hybridoma cells during the preparation of monoclonal antibodies to prokaryotic and eukaryotic ribosomal proteins. These monospecific antibodies will be utilized in the immunoelectronmicroscopic determination of ribosome structure. 2) Separate cells bearing specific antigenic markers such as Thy-1 and Lyt 1, 2 and 3. Separated populations may be utilized to study the ontogeny of thymus cell functions, the differentiation of T-cells, the ontogeny of supressor cells, selection of hybrid cells expressing particular gene activities, and endothelial cell identification. 3) Purify cells expressing particular genetic markers. 4) Separate chromosomes by shape and size.